Vikings built their houses like their ships -- up to 30 metres (100 feet) long with oval sides and sloping roofs. The main, boat-like room could house up to 50 people -- plus livestock in a freeze -- and was rimmed with bench beds around a central fireplace. Rough wooden plank walls, stacked vertically and woven together with wattle and daub, sealed out the cold and light. Heavy oak poles rimmed the outside, adding support to the walls. A thatched or sod roof with a hole in the centre supplied limited ventilation.
Mark out your longhouse, making sure the area is level. Sizes vary, but most longhouses big enough for an extended family and servants would be at least 4.3 metres (14 feet) wide and twice as long. Shape the layout of the house like a boat, with two arching sides joining each other at both ends.
Make a second line about 1.2 metres (4 feet) inside the perimeter line to mark the edge of the benches that will rim the inside wall.
Dig holes about 90 cm (3 feet) deep, every 1.8 metres (6 feet) around the perimeter of your building, large enough to hold the framing posts.
Set posts in the holes. Notch crossbeams where they line up with the tops of the posts and fit them together tightly. Lash the beams and posts together with green branches.
Pack the earth around your framing posts.
Lash pre-cut rough timber on to the wooden frame with green twigs. Stand every plank vertically in a tight row.
Daub thick mud into the joints between the boards to seal out weather.
Leave a 1.8 metre (6 feet) gap in the middle of one wall to extend into a square entrance.
Build frames for benches that will line the insides of both walls and clad the frames with rough timber. The benches should be about thigh high and extend directly inside from the wall about 1.2 metres (4 feet).
Roof the longhouse
Join two pairs of roof joists on the ground. Hoist them above the two widest points of the building, before the room tapers down at both ends. Secure the two roof joists upright with temporary posts.
Raise your pre-cut centre beam between the tops of both end joists and attach all three sections together securely. Sturdy tongue-and-groove construction techniques were unearthed in the longhouses of Trelleborg Viking fortress, Denmark.
Attach all other roof joists to the centre beam, spaced about 90 cm (3 feet) apart.
Lay two more beams from the centre beam to the opposing points, and attach shorter roof joists to complete the boat-shaped roof frame.
Weave branches between the joists to support the outer roof layer.
Viking houses were notoriously dark and fouled by smoke from cooking and oil lamps. Their windows were small and made of sheepskin. So consider any gaps or shortcomings in your building an opportunity for some much-needed light and air.
A lot of heavy lifting and possibly heavy equipment could be involved in building a Viking house. Make sure workers are qualified for the equipment they are operating and are conscientious about safety.